The IrDA (Infrared Data Association) protocol disclosed in Non-patent Document 1 is known as a protocol defined by the standard of short-range exchange of data over infrared light. The IrDA protocol involves an advance preparation for initiating transmission/reception of data, using a plurality of packets.
On the other hand, the IrSimple protocol was developed as an improvement of the IrDA protocol, in order to increase the efficiency of communication and the transfer rate. In the data communication using the IrSimple protocol, as shown in FIG. 5, a transmitting device to transmit data first transmits an SNRM (Set Normal Response Mode)—Command-Frame (IrSimple) packet (hereinafter referred to as an SNRM packet) 30, to a receiving device to receive the data. When the receiving device is compatible with the IrSimple protocol, the receiving device receives the SNRM packet 30 and thereafter sends a response to this SNRM packet 30 to the transmitting device. With this, transmission/reception of data based on the IrSimple protocol is initiated between the transmitting device and the receiving device. For taking account of a case where the receiving device is not ready to receive the data yet upon the transmission of the SNRM packet 30 to the receiving device, another SNRM packet 32 is again transmitted from the transmitting device to the receiving device after an after-described XID one-slot packet 40 is transmitted from the transmitting device to the receiving device.
After the foregoing SNRM packet 30, the transmitting device transmits to the receiving device, a Discovery-XID-Cmd packet (hereinafter referred to as an XID one-slot packet) 40 using one slot (i.e., being one slot) with the least significant two bits of 00 in Discovery Flags. When the receiving device is compatible with this XID one-slot packet 40 (i.e., when it is compatible with one slot), the receiving device sends a response to this XID one-slot packet 40 to the transmitting device. With this, transmission/reception of data based on the IrDA protocol is initiated between the transmitting device and the receiving device.
Non-patent Document 1: Infrared Data Association, “Serial Infrared Link Access Protocol (IrLAP),” (USA), Jun. 16, 1996, Version 1.1